查看更多>>摘要：The design of the excellent photocatalyst with high catalytic activity and light response characteristics remains a significant challenge for heavy metal reduction. Different from conventional heterostructures, this work focuses on a simple and feasible atomic-hybridized strategy to accelerate reaction kinetic process through constructing an electronic channel. Herein, we present an interesting molecule tailoring method to open C = O double bonds of carbon quantum dots (CQDs) and then anchor it onto ReS2 nanosheets to form an electronic channel via Re-5d and O-2p orbital hybridization, in which photoinduced carrier of surface-reduced CQDs (rCQDs) can freely transfer to ReS2 for hexavalent chromium reduction. Compared to pristine ReS2 nanosheets and CQDs/ReS2, the reduction reaction rate constant over the pseudo-first-order kinetic model is enhanced about 13.1 and 4.3 times, respectively. Our findings provide new inspirations for steering electronic channel by atomic hybridization and accelerating reaction kinetic mechanism simultaneously.
查看更多>>摘要：The catalytic hydrogen transfer (CHT) cascade reaction between alcohols and nitro- compounds meets green chemistry yet involves high catalyst requirements. Herein, a hierarchical nano-pyramid structure, in which cobalt single atoms (Co SAs) are deposited on highly dispersed ZnO nanoparticles supported by nitrogen-doped carbon (denoted as Co-ZnO/NC), was designed and obtained through pyrolysis of ZnCo-ZIF. The catalyst exhibited excellent catalytic performance toward the CHT cascade reaction, achieving a high nitrobenzene conversion (94 %), imine selectivity (97 %), and turnover frequency (8.8 h-1). This nano-pyramid is a state-ofthe-art non-noble-metal catalyst and is comparable to noble-metal catalysts. Experimental and DFT results revealed that the Co SAs supported on ZnO reduced the reaction energy barrier of hydroxyl dehydrogenation, the first and rate-determining step in this heterogeneous catalysis. Furthermore, Co-ZnO/NC exhibits good recyclability and universality. Our findings offer a new catalyst for Schiff base synthesis and aid understanding of the roles of Zn in ZIF-derived carbon catalysts.
查看更多>>摘要：A novel 3D printed photocatalytic feed spacer was developed for use in membrane-based water and wastewater filtration systems. The spacer fulfilled two new functions; degradation of membrane-permeating pollutants in the feed and membrane cleaning, in addition to its basic role as membrane support. The spacer, designed based on a triply periodic minimal surface architecture, was coated with polydopamine-polyethyleneimine, on which a photocatalytic layer of beta-FeOOH nanorods was mineralized. The photocatalytic performance of the spacer was demonstrated through the degradation of methylene blue and 4-nitrophenol, both in batch and crossflow ultrafiltration (UF) modes. The spacer also exhibited the ability to clean the membrane surface of three organic foulants (humic acid (HA), sodium alginate (SA) and bovine serum albumin (BSA)), with a flux recovery ratio of 92 %, 60 %, and 54 % achieved for SA, HA, and BSA, respectively. This enables a shift to spacer-centered photocatalytic membrane system approach in water and wastewater treatment.
查看更多>>摘要：It is extremely desirable to explore molecular catalysts with precise structure for in-depth exploring structureactivity relationship of CO2 photoreduction. Herein, we demonstrate the precise encapsulation of dual-nuclear clusters {Fe2(H2O)6(triazole)3} into metal-organic frameworks (MOFs) via ligand substitution strategy, resulting in two Fe2@Fe3-MOF composites (Fe3-Fe2 and NH2-Fe3-Fe2). The fixed distance between two adjacent Fe3(mu 3O)Cl(H2O)2 nodes in the MOF matrix allows the Fe2-Tri clusters to be fixed at a predetermined distance to unveil the critical role in improving the activity and selectivity for CO2 reduction. The performance of Fe3-Fe2 and NH2Fe3-Fe2 can reach to 309.3 and 395.5 mu mol g-1 h-1 respectively, much superior to most of the state-of-the-art MOF catalysts. Such high activity and selectivity for formate generation can be attributed to the inter-clusters synergy mediated via in situ formed H-bonds and the cluster-framework cooperativity, supported by the results of DFT calculations and systemic experimental characterizations.
查看更多>>摘要：Development of low-cost, high-performance photocatalysts for the effective degradation of antibiotics in wastewater is critical for environmental remediation. In this work, titanium dioxide/zirconium dioxide/graphitic carbon nitride (TiO2/ZrO2/g-C3N4) ternary composites are fabricated via a facile hydrothermal procedure, and photocatalytically active towards the degradation of berberine hydrochloride under visible light illumination. The performance is found to increase with the Ti:Zr atomic ratio in the nanocomposites, and obviously enhanced in comparison to that of the binary TiO2/g-C3N4 counterpart, due to the formation of type I/II heterojunctions that help separate the photogenerated electron-hole pairs and produce superoxide and hydroxy radicals. The mechanistic pathways are unraveled by a deliberate integration of liquid chromatography-mass spectrometry measurements with theoretical calculations of the condensed Fukui index. Furthermore, the ecotoxicity of the reaction intermediates is examined by utilizing the Toxicity Estimation Software Tool (TEST) and quantitative structure activity relationship calculations (QSAR).
查看更多>>摘要：Ammonia (NH3) as an important precursor to form atmospheric fine particles and secondary inorganic aerosols, should be strictly controlled. Photocatalysis has provided a facile and an effective way to eliminate NH3 pollution under mild conditions, whereas the undesirable products, such as NO, NO2 would be generated during the reaction and the mechanism remains unclear. In this study, F or Pt modified TiO2 were explored to reduce the formation of NOx during photocatalytic oxidation of low-concentration NH3, and its photocatalytic activity, selectivity and mechanism of NH3 conversion were systematically studied. Results indicate that surface fluorination on TiO2 contribute to the reduction of noxious NOx, especially for NO2, since the modified TiO2 achieved enhanced adsorption of NH3 and strong electron-trapping ability, which can retard the recombination of photo generated electrons and holes. In addition, the deposition of Pt could further extend the lifetime of the electron hole pairs by strongly capture the electron, and enhance the oxidation of NH3 into nitrates and nitrites species. From the in-situ DRIFT spectroscopy and XPS results, we can deduce that reactive amino radical (center dot NH2) would be formed on TiO2 under photoirradiation after the adsorption of NH3 on Lewis acid cites. The formed center dot NH2 can react with reactive oxygen species in the presence of H2O, and produce NOx and HNOx. By both enhancing the adsorption of NH3 and separation efficiency of electron-hole pairs, the presence of F and Pt modification on the TiO2 changes the photocatalytic pathway of NH3 conversion. The proposed selective oxidation mechanism may offer a novel insight into the photocatalytic oxidation of atmospheric NH3 on other metal oxide with surface modification and can be broadly employed in air pollution control in indoor environments.
查看更多>>摘要：Photocatalytic visible water splitting is still impeded by slow kinetics of multi-electron-driven water oxidation, fast carrier recombination and insufficient light absorption of the photocatalyst. Herein, the core-shell heterojunction BxGa1_xAs/GaAs photocatalyst exhibited a remarkably promoted activity for hydrogen generation by direct dissociation of water molecule over boron site on catalyst surface due to redistributing electron density, as well as by promotion of visible absorption and acceleration of charge separation and transfer via a built-in electric field. B0.25Ga0.75As/GaAs photocatalyst exhibited hydrogen evolution rate of 8.4 mu mol during 8 h from pure water without electron donor and applied bias.
查看更多>>摘要：Cobalt species as active sites for photocatalytic reduction of CO2 to valuable products such as methanol have received increasing attention, however, it remains a huge challenge to achieve the high activity. Herein, a pyrolysis-induced-vaporization strategy was successfully employed to fabricate Co/g-C3N4 single-atom catalysts (Co/g-C3N4 SACs) with surface Co atom loading up to 24.6 wt%. Systematic investigation of Co/g-C3N4 SACs formation process disclosed that concentrated-H2SO4 exfoliation of g-C3N4 nanosheets (g-C3N4 NSs) as the substrate followed by a two-step calcination process is essential to achieve ultrahigh metal loading. It was found that the ultrahigh-density of Co single-atom sites were anchored on the g-C3N4 substrate surface and coordinated with two nitrogen and one carbon atoms (Co-N2C). These single dispersed Co-N2C sites on the g-C3N4 surface were found to act not only as electron gathering centers but also as the sites of CO2 adsorption and activation, subsequently, boosting the photocatalytic methanol generation during light irradiation. As a result, the methanol formation rate at 4 h (941.9 mu mol g(-1)) over Co/g-C3N4-0.2 SAC with 24.6 wt% surface Co loading was 13.4 and 2.2 times higher than those of g-C3N4 (17.7 mu mol g(-1)) and aggregated CoOx/g-C3N4-0.2 (423.9 mu mol g(-1)), respectively. Simultaneously, H-2 (18.9 mu mol g(-1) h(-1)), CO (2.9 mu mol g(-1) h(-1)), CH4 (3.4 mu mol g(-1) h(-1)), C2H4 (1.1 mu mol g(-1) h(-1)), C3H6 (1.4 mu mol g(-1) h(-1)), and CH3OCH3 (3.3 mu mol g(-1) h(-1)) products were detected over Co/gC(3)N(4)-0.2 SAC. Besides, the photocatalytic activity of the Co/g-C3N4-0.2 SAC for the reduction of CO2 to methanol was stable within 12-cycle experiments (similar to 48 h). This work paves a strategy to boost the photoreduction CO2 activity via loading ultrahigh surface density single atomically dispersed cobalt active sites.
查看更多>>摘要：The metallic polymorph of molybdenum disulfide (1T-MoS2) is a promising catalyst towards the hydrogen evolution reaction (HER). However, the intrinsic activity on basal plane is significantly inferior to that at edges despite the dominate number of basal plane atoms. Herein, we conducted an activation engineering to enhance the catalytic activity of the basal plane by constructing in-plane heterostructure with CoS2 nanodomains embedded in 1T-MoS2 basal plane (CoS2@1T-MoS2). Experimental and DFT analysis demonstrates a charge transfer from both CoS2 and 1T-MoS2 to the interface, which enables the formation of electron rich sites with high activity. Moreover, the in-plane heterostructure fully exposes the heterogeneous interfaces and promotes the accessibility of active sites. Consequently, the CoS2@1T-MoS2 delivers an excellent performance towards the HER with an overpotential of 72 mV at 10 mA.cm(-2), Tafel slope of 45 mV.dec(-1) as well as remarkable stability. This work proposes a strategy to design highly efficient electrocatalysts based on 1T-MoS2.
Kapuge, Tharindu KankanamGrankina, VeraNandi, ParthaSuib, Steven L....
13页
查看更多>>摘要：We report an aerobic partial oxidation of isobutylene into isoprene, acetone, and para-xylene using a mesoporous Ni TiOx catalytic material. In this work, two catalysts were found to synthesize two of these three valuable products with high selectivity, with p-xylene being synthesized with a selectivity of 46.0% and isoprene being synthesized with a selectivity of 64.7%, with overall conversions of isobutylene being 34.0% and 11.9% respectively. These reactions were done at relatively low temperatures (300 degrees C or below) and are conducted at flow rates of 10 sccm oxygen and isobutylene. The nickel titania catalysts were studied extensively using various characterization methodologies such as TEM, Raman, XRD, and XRF.
NSTL
Elsevier